1. Field of the Invention
The present invention relates to improvements to motor driven operators for high voltage switches, and more particularly, the present invention relates to means for preventing a manually operable crank handle from engaging a switch operating mechanism until stored energy has been released and means for disconnecting the drive shaft and locking the drive shaft of a switch operating mechanism when maintenance or testing is to be performed.
2. Description of the Prior Art
The present invention comprises improvements to the switch operating mechanism disclosed in U.S. Pat. No. 3,508,179 -- Bernatt et al., issued Apr. 21, 1970. Motor driven operating mechanisms for high voltage switches are well known in the art. Such mechanisms are also disclosed in U.S. Pat. No. 3,432,780 -- Evans et al., issued Mar. 11, 1969. Typically, such switch operating mechanisms are motor driven and controlled by remotely located control circuitry which causes automatic operation of the switch operating mechanism in response to appropriate control signals from the control circuitry. For example, the control circuitry may be designed to sense fault conditions in the electrical transmission system so that the high voltage switches are rapidly operated to open the high voltage circuit when a fault condition exists. However, although the high voltage switch is usually remotely controlled, it is desirable to also provide a means for manually operating the switch operator at a location adjacent the high voltage switches. Further, it is often desirable to disconnect the operating mechanism from the high voltage switches so that the mechanism can be tested and maintenance performed without the necessity of operating the high voltage switches and thereby interrupting the high voltage circuit.
Since the high voltage switches are typically interconnected by long drive and interphase shafts, and since the mechanism is ordinarily driven by a motor driving through a gear train having a substantial gear reduction so that substantial torgue is imparted to the system, the drive shaft and interphase shafts typically are placed under torsional stress when the switch is operated. A brake mechanism is usually provided which locks the motor immediately after power is removed so that the torsional energy remains stored in the system until released when the brake is released.
When manual operation is desired, a crank handle is typically connected to the mechanism and the brake is released so that the switches can be operated manually. However, when the brake is released, the torsional energy stored in the system is also released, sometimes causing a rapid whipping of the manually operable crank handle which may harm the operator. Accordingly, it would be a desirable advance in the art to provide a means for preventing engagement of the crank handle with the mechanism until the torsional energy has been released thereby avoiding possible unexpected whipping of the crank handle.
Further, since high voltage switches are typically mounted well above ground on towerlike supports, these switches experience externally applied forces resulting from wind and vibration. Accordingly, unless the drive shaft is locked, it is possible for the switches to inadvertently and accidentally move from a closed position to an opened position or vice versa when such movement is not desirable. Accordingly, it would be a desirable advance in the art to provide an improved means for locking the drive shaft whenever the drive shaft is disconnected from the operating mechanism so that maintenance and testing can be performed on the switch operating mechanism without the risk of the high voltage switches accidentally opening or closing.